Certain conventional loading and unloading units of sheet metal processing systems are capable of performing multiple functions. In some cases, a loading and unloading unit is used to provide a sheet-metal processing machine with workpieces (e.g., sheets) to be processed. The loading and unloading unit can also be used to transfer processing tools between a linear magazine of the processing machine and a tool store provided on a frame of the loading and unloading unit. In order to change a tool, the loading and unloading unit includes a tool change apparatus in the form of a pincer-like gripper. With suitable travel, the loading and unloading unit moves the gripper relative to a tool carrier of the machine-side linear magazine or relative to a tool carrier in the store into a tool change position in which a processing tool can be delivered by the gripper to the relevant tool carrier or can be removed by the gripper from the relevant tool carrier. A functionally reliable tool change can benefit from accurate mutual positioning of the gripper and of the relevant tool carrier. The tool change position of the gripper is typically stored in the numerical control of the sheet metal processing system. Using the stored position, the gripper is transferred into the tool change position by the loading and unloading unit with a controlled positioning movement. In defining the tool change position, both the gripper and the tool carrier to be served are assumed to have a nominal position.